Iodine Recommendations

Customer:

“I’ve been giving my horses Horse Guard for years and I use free feed salt. Normally I just use straight un-iodized salt figuring they get the iodine they need in the Horse Guard. My feed store was out of the stuff I normally buy & very highly recommended Redmond Salt. The warehouse guy accidentally gave me the high iodized bag. Luckily I read the label before I opened it & saw the iodine levels (it’s for cattle), but I noticed a warning that said not to allow more than 1/4 oz per head per day or you’d go over the 10mg/head/day max recommended dose. What is the recommended Iodine dose for a horse? Is it the 10mg or is that just for cattle? What about all of the other stuff? I’d just as soon give them the Redmond Salt that’s not processed, but I’m over my head on the trace mineral stuff.”

Answer from Equine Nutritionist, Del Johnson:

Thanks for your questions about iodized salt.

1989 NRC on equines estimated that the iodine requirement of horses 1 to 6 mg per day for a 1000 lb horse.

The maximal tolerable dietary concentration of iodine has been estimated to be 50 mg of iodine/day for a 1000 lb horse.

The guarantee for iodine in salt is by weight in ounces not volume. A product that provides 100 ppm has 100 mg in 2.2 lbs. That works out to 2.84 mg of iodine per ounce. Salt that is 10 parts per million would provide .284 mg of iodine per ounce.

Horses will eat 1 ounce of salt per day on average. This is a dangerous assumption if your trace mineral is in the salt because consumption varies from 0 ounces of salt per day to over 3 ounces per day. The reason for the variance is complex. Horses working hard and sweating will require more salt. Horses on hay that has been salted will not consume salt. If it is hot they will eat more, cold they eat less. Salt, like water, is a nutrient that animals actually select to fulfill their requirement….this is not true of other nutrients.

My recommendation is that you provide plain salt without additives – free choice. Having said that most iodized and trace mineral salt provides so little of these nutrients that they do not cause a problem.